1. Field of the Invention
The present invention relates to the field of semiconductor processing equipment and, more particularly, to a technique of monitoring voltage and current for control of an ongoing semiconductor process.
2. Prior Art
In the fabrication and processing of semiconductor wafers, such as silicon wafers, a variety of different semiconductor equipment and processes are utilized. The wafer processing techniques are well known in the prior art and include photolithography, deposition, etch, as well as a variety of other processes. Furthermore a variety of sensors and control equipment are associated with metrology for determining the performance of tools in the various manufacturing steps. Although equipment and process steps have improved over the years, the technique of monitoring the ongoing process has not necessarily kept pace with the other improvements. In the field of monitoring the ongoing semiconductor process, current practices generally rely on ex-situ monitoring. A problem with ex-situ monitoring is that the results are not available until the end of the process or, if intermediate readings are required, the ongoing process must necessarily be interrupted in order to obtain the required reading.
In the area of radio frequency (RF) signal monitoring, the art abounds with various devices and techniques for measuring a RF signal. However, in many instances, it is difficult to couple a particular sensor to obtain an accurate measurement of the RF signal. Sometimes, such RF monitors disrupt the process or fail to obtain accurate indications of the ongoing process. This is especially so with RF measurements of plasma reactors. Additionally, such techniques are not generally practiced in order to provide in-situ control of an ongoing manufacturing process. As stated above, complications are further heightened when invasive probes are utilized in a plasma reactor chamber.
The present invention provides for a RF monitor and a scheme for utilizing the RF monitor to control a plasma process. The RF monitoring device can be implemented economically, but without interfering with the plasma process.